This application claims the priority of Korean Patent Application No. 2004-112066, filed on Dec. 24, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a mobile communication terminal and, more particularly, to a mobile communication terminal capable of displaying a power-off charging condition.
2. Description of Related Art
Mobile communication terminals providing power-on and power-off charging functions have been currently put on the market at the request of mobile carriers. The power-on charging function implies that when a mobile communication terminal is charged through a charging jack during power-on of the mobile communication terminal, a charging condition is displayed on a display unit of the mobile communication terminal. The power-terminal. The power-off charging function implies that when a mobile communication terminal is charged through a charging jack during power-off of the mobile communication terminal, the mobile communication terminal is powered on and a charging condition is displayed on a display unit of the mobile communication terminal. During a power-on charging condition, the mobile communication terminal provides all functions incorporated therein. However, during a power-off charging condition, the mobile communication terminal provides the power-off charging function but cannot provide other functions. Meanwhile, during the power-off charging condition, there is an advantage in that unnecessary battery consumption is avoided.
FIG. 1 is a schematic circuit diagram of a conventional construction configured to display a power-off charging condition in a mobile communication terminal. When a user presses a switch_on key during power-off of a mobile communication terminal, a signal of the switch_on key ON_SW is inputted to an EN terminal of a DC-DC converter. When the user presses the switch_on key ON_SW during power-off of the mobile communication terminal, a switch connected to a battery and the EN terminal of the DC-DC converter is switched on so that voltage applied from the battery is supplied to the EN terminal. When the voltage is supplied to the EN terminal, the DC-DC converter is activated, adjusts the voltage VBATT applied from the battery to a voltage V_MSM having a level suitable for the mobile communication terminal, and supplies the voltage V_MSM to a controller controlling the mobile communication terminal. The controller outputs a signal PS_HOLD to the EN terminal of the DC-DC converter to obtain an effect of continuously pressing the switch_on key ON_SW. The controller controls the mobile communication terminal using the voltage supplied from the battery. If the user connects a charging jack of a battery charger to the mobile communication terminal which is powered on, it implies that the mobile communication terminal is in the power-on charging condition.
Meanwhile, when the user powers off the mobile communication terminal, the controller performs a power-off process of the mobile communication terminal and stops outputting the PS_HOLD signal to the EN terminal of the DC-DC converter. Consequently, voltage is not supplied from the battery to the controller, thereby powering off the mobile communication terminal. During power-off of the mobile communication terminal, when the user connects a charging jack of a battery charger to the mobile communication terminal, the battery charger charges the battery through the charging terminal and the voltage VCHARGER is supplied to the EN terminal of the DC-DC converter. As a result, the voltage VBATT from the battery is supplied to the controller through the DC-DC converter and the mobile communication terminal is powered on. That is, the mobile communication terminal is in the power-off charging condition.
However, when a user connects the charging jack of the battery charger to the mobile communication terminal during powering-off of the mobile communication terminal, the PS_HOLD signal is in a low state but the voltage VCHARGER of the battery charger is supplied to the EN terminal of the DC-DC converter, whereby the voltage from the battery is supplied to the controller. As a result, there is a problem in that the controller cannot perform the power-off process normally and the mobile communication terminal may stop operating.